repo: Add unconfigured-state to remote config options

This is a migration from the origin version.  It's
nicer to have it in the remote, since that's what one
needs to change.  Then tools don't need to mess with
the origin file.o

In fact in this scenario one can keep the "media source" like
`file:///install/repo` or whatever, since conceptually that's where it
came from.  We're just providing a better error.

Closes: https://github.com/ostreedev/ostree/issues/626

Closes: #627
Approved by: jlebon

src/libostree/ostree-sysroot-upgrader.c

@@ -77,7 +77,9 @@ parse_refspec (OstreeSysrootUpgrader  *self,
 
   if ((self->flags & OSTREE_SYSROOT_UPGRADER_FLAGS_IGNORE_UNCONFIGURED) == 0)
     {
-      /* If explicit action by the OS creator is requried to upgrade, print their text as an error */
+      /* If explicit action by the OS creator is requried to upgrade, print their text as an error.
+       * NOTE: If changing this, see the matching implementation in ostree-repo-pull.c.
+       */
       unconfigured_state = g_key_file_get_string (self->origin, "origin", "unconfigured-state", NULL);
       if (unconfigured_state)
         {